When SD (Standard Definition) video is scaled to HD (High Definition) resolution, video images tend to look blurred. Video/image sharpness may also get lost due to the encoding and a variety of processing such as noise reduction, de-ringing, or de-blocking. Edge and Detail enhancement (EDE) is typically used to improve the image resolution and perceived sharpness by recovering the lost high frequency information or boosting the high frequency information.
LTI/CTI (Luminance Transient Improvement and Chrominance Transient Improvement) and peaking are both techniques aiming at improving image sharpness. LTI (CTI) typically steepens the Luma/Chroma transition slope by shrinking the width of the transients or moving the pixels in the slope transitions towards the edge center. The peaking filters usually use a linear filter (typically an FIR filter) plus the clipping and coring techniques to boost the high frequency signals. So peaking is usually a linear technique (except for the clipping and coring part) for EDE, and LTI/CTI are nonlinear techniques. Note that peaking is to amplify the high frequency information of the original signals, while LTI (CTI) may recreate the high frequency information to make pictures look sharper. So special care needs to be taken care of when LTI/CTI is used, as it is more likely to introduce unexpected artifacts.